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When it comes to your monthly flow, unexpected intermissions can be quite an unwelcome surprise, especially if getting pregnant is not on your to-do list.

If you’d rather be without child for the near future, it’s important to stay on top of your cycle and fertility to avoid any baby bumps in the road, as it were. Here are a few ways to stay menstrual-ly responsible.

So you got your period… and now you want to know when it’s safe to have unprotected sex. NEVER! Just kidding (kind of). While only protected sex can offer the kind of assurance you might be after, there are ways to track your fertility throughout the month.

The truth is that you’re not fertile every day of the month. Tracking your fertility can be a bit of a balancing act. To stay safe, you have to know when you’re ovulating.

Ovulation typically occurs between days 11 and 21 of a menstral cycle when a fertile egg is released, but it actually only happens for just one day — wild, right? Even crazier, the egg only lives for about 4 to 12 hours.

So, outside this ten-ish day window where you might be ovulating (more on that later), you actually can’t get pregnant. Keep in mind, sperm can live in the body for around 3 to 5 days, so that can widen your window a bit.

The more regular your period, the easier it is to track your fertility and know your fertility window. The average cycle lasts 28 to 30 days, and many women ovulate smack dab in the middle at day 14. That being said, there’s a veritable buffet of tools and methods to help you narrow it down.

Finding your window: 101

As with many things, there are now quick fixes. Tracking your fertility window accurately can be quite the time investment, but consider it the price for your sanity every month. Here’s a step-by-step guide to the process:

Record the start date and duration of your period for 8 to 12 months. Consider day one the first day of your period.

Take note of your longest and shortest cycle.

Next, take your shortest cycle and subtract 18 days — that’s the first day of your fertile window. So if your shortest cycle was 28 days, yours would be day 10.

Now subtract 11 days from the duration of your longest cycle. If it was 31 days, you would write down day 20.

Your fertile window is the time between the 2 days you wrote down. Based on the above examples, that would be between day 10 and 20. Consider that period of time a no-fly zone for unprotected sex if you want to avoid getting pregnant.

Go hi-tech

When it comes to tracking your fertility, there’s an app for that. In fact, there are many. Many come with added bonus features that can help track your menstrual symptoms and the days you had sex. Here are a few fan favorites:

Fertility Friend App

This advanced tracker uses your data to drum up a personalized fertility chart. Fertility Friend App will send you a notification on your ovulation days and send you tips and rundowns of your data for those trying to conceive.

Ovia Fertility & Cycle Tracker

Ovia is a great option if you have irregular periods. Its algorithm helps you accurately track your period and fertility window. Ovia also offers other tips and statistics for all things menstrual (symptoms, period length, etc.), in addition to customized fertility charts with trends and insights.

Glow: Fertility Calculator and Ovulations

Glow’s ovulation calculator helps you track of your cycle and any sexual activity or symptoms you may experience throughout the month. While it’s typically used to help women get pregnant, you can use this information to practice baby-free sex.

Period Tracker by GP Apps

iPhone rating: 4.8 stars

This easy-to-use app helps you predict your next period as well as ovulation. You can track all sorts of other relevant information too, like sexual activity, temperature, and weight.

As mentioned above, having regular cycles can make a world of difference in effectively tracking your cycles. Everybody and every body is different. And external factors can throw a wrench in your monthly regularity.

Heavy exercise, diet, and stress all play a part in the length of your cycle. So keep in mind that the day of your ovulation isn’t written in stone.

While tracking your fertility window may help keep pregnancy at bay, it’s actually more effective at getting a baby on board. If you really want to avoid getting pregnant, don’t have unsafe sex and talk to your doctor about birth control.

If tracking your fertility by keeping tabs on your cycle just doesn’t work for you, there are some other options you can try.

The temperature method

Getting to know your basal body temperature can help you know when your body is ovulating. Your basal body temperature is your body’s standard temperature while fully at rest, and it spikes slightly just after you ovulate.

Keep in mind, this method requires reinforcements, specifically a special basal temperature thermometer. Keep track of your temperature first thing when you wake up, before you start moving about.

During ovulation, it should rise ever so slightly, by 0.5°F (0.3°C). If you’re trying to put off pregnancy, it’s best to hit pause on any unprotected sex for at least a couple of days after this rise in temperature.

The cervical mucus method

When you ovulate, your estrogen levels increase, which causes your cervix to produce mucus. Some women may notice clear and stretchy mucus (think egg whites) close to ovulation, when they’re most fertile.

The calendar method

To do the calendar method, you’re going to need to track at least six of your cycles. If all your cycles are shorter than 27 days, this won’t be an accurate method for you.

The following process will look very familiar to what was outlined above. Start by noting the first calendar day of your flow (day one). Next, note the first day of your next period. Then, count the number of days between each cycle start day.

Subtract 11 days from the duration of your longest cycle, and 18 days from the shortest one. This represents the first and last day of your fertility window.

Let’s say your longest cycle was 30 days. Based on this method, you get 19. So, if your period started on the 3rd of the month, you’d mark the 22nd of that month as the last day of your fertility window, and you should wait at least a couple of days to have unprotected sex.

The calendar method isn’t 100 percent reliable, nor is it an exact science. It’s best to combine it with other methods to stay safe.

The standard days method

The Standard Days method is sort of like a streamlined calendar method. It only works if your menstrual cycle is incredibly regular — as in, your cycles are never shorter than 26 days or longer than 32.

According to the Standard Days method, you simply refrain from vaginal sex on days 8 to 19 of your cycle. Mind you, other kinds of birth control (like condoms) are always an option on those days.

You might find it helpful to rely on an app to help you keep track of your cycle with the Standard Days method. A lot of women opt for CycleBeads, which are exactly what they sound like: a string of 33 colored beads with a black rubber band that you can adjust from bead to bead.

As intimate and fun as unprotected sex with a partner can be, it’s important to consider the risks attached — pregnancy and otherwise. Only you know what’s best for you, but it can’t hurt to maintain an open dialogue with your partner as well (not to mention your doctor) when it comes to pregnancy prevention.